This invention relates to a magnetic record member for use in magnetic recording devices such as a magnetic disc and magnetic drum.
Magnetic recording and reproducing systems utilizing record/playback heads and magnetic record members (e.g. magnetic disks) may be classified into two general systems. In the first system, a record or playback operation is initiated by bringing the record/playback head into contact with the surface of a magnetic record member and thereafter rotating the record member at a given r.p.m. As a result of this operation, a protective air layer is formed between the head and the surface of the magnetic record member during the record or playback operation. The foregoing start-stop system will hereinafter be referred to as CSS. Upon the completion of a record or playback operation, the rotation of the magnetic record member is stopped while the head and record member are still in frictional contact with each other.
In the second system, the magnetic record member is rotated at a given r.p.m. before the head is brought into contact with the surface of the record member. Again a protective air layer is formed between the head and the magnetic record member during the record and playback operations. In summary, the first class of systems bring the head into frictional contact with the record member both at the start and at the termination of a record or playback operation. In the second system, the head is brought into frictional contact with the record member when it is urged against the surface of the latter at the initiation of a record or playback operation. Such frictional contact between the head and the magnetic record member results in wear of the head and magnetic record member, and eventually harms both the head and a magnetic metal thin film medium formed on the record member. Another problem caused by the foregoing frictional contact is that slight variations in attitude of the head results in a lack of uniformity of the load imposed on the head causing damage to both the head and the surface of the record member. The foregoing problems are compounded during the record or playback due to the fact that the head occasionally contacts the record member resulting in large frictional forces between the head and the record member. In order to minimize damage to both the head and the record member resulting from the foregoing frictional forces, a protective film should be provided on the surface of the magnetic record member. To this end, the prior art has utilized plated metal films such as Cr, Rh, Ni-P and the like. Such films have not been provided adequate protection.
An alternative film is disclosed in U.S. Pat. No. 3,466,156. In accordance with this patent, a synthesized polymer thin film is formed on a magnetic metal thin film medium, and a thin wax film formed on the metal thin film medium. While this film has provided improved protection for the record member, the synthesized polymer thin film and the wax film fail to form a sufficient adhesive bond to the underlayer. As a result, they tend to peel off the underlayer due to repeated friction contact between the head and the magnetic record member.
Yet another protective layer is disclosed in U.S. Pat. No. 3,719,525. In this patent, the protective layer comprises an oxidized magnetic metal thin film medium to which silicone oil has been applied. The drawback of this protective film is that it impairs the magnetic characteristics of a magnetic thin film applied to the record member. Additionally, this protective layer also exhibits the adhesion problem noted with respect to U.S. Pat. No. 3,466,156 noted above.
The inventor has proposed a magnetic record member having a protective film consisting of a polysilicate film coated on a magnetic metal thin film medium or an oriented lubricant coated on the aforesaid polysilicate film (see U.S. patent application Ser. Nos. 700,191 and 734,962 filed on June 28, 1976 and Oct. 22, 1976, respectively). While this protective film has been satisfactory for most applications, it is desirable to provide an even more reliable protective layer.